How to compare with optimal effort whether 2 JAVA NESTED COLLECTIONS of this format List<Map<String, Object>> are equal

How to compare with optimal effort whether 2 JAVA NESTED COLLECTIONS of this format List<Map<String, Object>> are equal

In List<Map<String, Object>> the Object can be List or Map

I need to write unit tests to compare the values of nested collection object parsed from a json and the expected value (another collection which I manually create).
I can do this iteratively by going deep to each of the objects and compare them against the values from the other collection.

But this approach seems to be very tedious since I have to iterate each different test cases.

Is there any other efficient approach?

This is exactly what assertEquals is for.

assertEquals(expected, actual);

The will make it difficult to debug when things go wrong though.

Depending on how your code is structured, you might be better off using a mock for the json parsing part, and validating only that your code is passing in the expected values to the parser.

If nothing else, instead of building up the second collection, why not just assert the values there? If you're manually "creating" the expected collection, you can instead manually check the returned collection.

As pointed out by @Holger this is kind of not efficient!

package im.silentsudo.gradletest;

import com.google.gson.Gson;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;
import org.junit.Assert;
import org.junit.Test;

import javax.xml.bind.DatatypeConverter;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class HashComparisionTest {

    @AllArgsConstructor
    @NoArgsConstructor
    static class Post {
        Long id;
        String title;
    }

    static private Map<String, Object> generateUser1PostList() {
        final List<ComparisionMain.Post> posts = new ArrayList<>();
        posts.add(new ComparisionMain.Post(1L, "Post 1"));
        posts.add(new ComparisionMain.Post(2L, "Post 2"));
        final Map<String, Object> userPosts = new HashMap<>();
        userPosts.put("user_a", posts);
        return userPosts;
    }

    static private Map<String, Object> generateUser2PostList() {
        final List<ComparisionMain.Post> posts = new ArrayList<>();
        posts.add(new ComparisionMain.Post(20L, "Post 20"));
        posts.add(new ComparisionMain.Post(21L, "Post 21"));
        final Map<String, Object> userPosts = new HashMap<>();
        userPosts.put("user_b", posts);
        return userPosts;
    }

    static private String getHash(String content) throws NoSuchAlgorithmException {
        MessageDigest messageDigest = MessageDigest.getInstance("MD5");
        messageDigest.update(content.getBytes());
        byte[] digiest = messageDigest.digest();
        return DatatypeConverter.printHexBinary(digiest);
    }


    @Test
    public void testTwoCollectionMeaningfullyEquals() throws NoSuchAlgorithmException {
        System.out.println("------------- testTwoCollectionMeaningfullyEquals --------------");
        final Gson gson = new Gson();
        List<Map<String, Object>> collection1 = new ArrayList<>();
        List<Map<String, Object>> collection2 = new ArrayList<>();

        collection1.add(generateUser1PostList());

        collection2.add(generateUser1PostList());

        final String hash1 = getHash(gson.toJson(collection1));

        System.out.println(hash1);
        final String hash2 = getHash(gson.toJson(collection2));
        System.out.println(hash2);

        Assert.assertEquals(hash1, hash2);

        System.out.println("------------- testTwoCollectionMeaningfullyEquals --------------");
    }

    @Test
    public void testTwoCollectionMeaningfullyNotEquals() throws NoSuchAlgorithmException {
        System.out.println("------------- testTwoCollectionMeaningfullyNotEquals --------------");
        final Gson gson = new Gson();
        List<Map<String, Object>> collection1 = new ArrayList<>();
        List<Map<String, Object>> collection2 = new ArrayList<>();

        collection1.add(generateUser1PostList());

        collection2.add(generateUser2PostList());

        final String hash1 = getHash(gson.toJson(collection1));

        System.out.println(hash1);
        final String hash2 = getHash(gson.toJson(collection2));
        System.out.println(hash2);

        Assert.assertNotEquals(hash1, hash2);

        System.out.println("------------- testTwoCollectionMeaningfullyNotEquals --------------");
    }
}

Output of the above program is:

Testing started at 12:01 PM ...
> Task :cleanTest
> Task :compileJava UP-TO-DATE
> Task :processResources NO-SOURCE
> Task :classes UP-TO-DATE
> Task :compileTestJava
> Task :processTestResources NO-SOURCE
> Task :testClasses
> Task :test
------------- testTwoCollectionMeaningfullyNotEquals --------------
766461F7DB37B8EC031BE0145E6832D3
156636D7A2CF2196783F9D644A994391
------------- testTwoCollectionMeaningfullyNotEquals --------------
------------- testTwoCollectionMeaningfullyEquals --------------
766461F7DB37B8EC031BE0145E6832D3
766461F7DB37B8EC031BE0145E6832D3
------------- testTwoCollectionMeaningfullyEquals --------------
BUILD SUCCESSFUL in 0s
4 actionable tasks: 3 executed, 1 up-to-date
12:01:49 PM: Tasks execution finished ':cleanTest :test --tests "im.silentsudo.gradletest.HashComparisionTest"'.

This is very simple implementation, if you need more details on object comparision in java please take a look at https://www.baeldung.com/java-equals-hashcode-contracts